This invention relates to a transistor circuit, and more particularly to an improved transistor circuit capable of preventing its wrong operation due to .alpha. rays and the like that are emitted from a trace amount of radioactive substances contained in a packaging material of a semiconductor.
A circuit configuration such as shown in FIG. 6 of the accompanying drawings has often been employed conventionally in those circuits which are composed of transistors. Circuits 15, 16 and a transistor 13 exist between a ground potential and a power supply voltage V.sub.EE and a vias V.sub.B1 is applied to the base of the transistor 13 so as to obtain a desired voltage V.sub.out from its collector. As a more definite example, FIG. 7 shows a constant current circuit. Namely, transistors 13, 13A and resistors 21, 24 form a constant current circuit and a constant voltage V.sub.out is obtained through an emitter follower 22. In comparison with the circuit shown in FIG. 6, the resistor 21 corresponds to the circuit 15.
However, this prior art technique does not take into consideration external noise, particularly the influences of .alpha. rays. If the .alpha. rays are incident to the transistor 13 in FIG. 6, critical influences are exerted on the voltage V.sub.out. In other words, a noise current flows from the collector of the transistor 13 to a substrate (not shown) of an integrated circuit when the .alpha. rays are incident to the transistor 13. Accordingly, particularly when the impedance of the circuit 15 is great, the voltage V.sub.out is temporarily reduced greatly from the set value. This noise causes a wrong operation of the circuit using the voltage V.sub.out. In FIG. 7, the noise current flows from the resistor 21 and the collector of the transistor 13 to the substrate with the result being the drop of the base potential of the transistor 22 as well as in the drop of the voltage V.sub.out.
Incidentally, the mechanism of the noise current due to the incidence of the .alpha. rays into the transistor is described in detail in U.S. Ser. No. 020,892 (filed on Mar. 2, 1987) and this reference proposes an improved flip-flop circuit which prevents the occurrence of soft errors by the .alpha. rays.